Tuesday, 15 September 2015
How is Paper Recycled
If you're anything like me, you probably did learn in grade school how paper is made and even how recycled paper comes into being. As the years have gone on however, I've entirely forgotten the process. But alas, my curiosity has led me to relearn how exactly paper gets recycled and well, here's how it happens:
First the waste paper needs to get sorted – whether it's newsprint, corrugated cardboard, magazine paper, etc. The different types of paper are sorted into their respective groups because different types of paper require different processes in order to be recycled.
Once sorted, the paper gets put into a huge vat called a pulper. Here the recovered paper soaks in water and chemicals and the pulper also chops the paper into smaller bits. Applying heat to the mixture helps to break the paper down more quickly into tiny strands of organic plant material called fibres. Eventually, the chopped up paper turns into a mushy mix called pulp.
Cleaning and Screening
The paper is then cleaned and screened. The process of screening involves forcing the pulp through screens with holes (like a sieve) to remove contaminants like bits of plastic or glue.
The pulp is further cleaned by being spun around a large cone-shaped cylinder which removes heavier contaminants like staples by throwing them to the outside of the cone which then fall through the bottom of the cylinder. Lighter contaminants collect in the centre of the cone and are then removed.
The next step is laundering the pulp which means removing ink from the paper fibres. Usually this is a two-step process. To de-ink paper, a combination of chemicals and water are used to rinse and remove small particles of ink.
For larger particles, a process called floatation is used. Floatation uses air and soap-like chemicals called surfactants to dislodge ink and sticky materials like glue and adhesives from the recovered paper. The surfactants cause these contaminants to loosen from the pulp and stick to the air bubbles as they float to the top of the mixture. The inky air bubbles then create a foam or froth which is then removed, leaving you with clean pulp.
Refining, Bleaching and Color Stripping
The refining process involves beating the pulp in order to make the fibres swell and separate – which is what you want when you're making recycled paper.
If the recovered paper is going to become white recycled paper, then the next part is bleaching the paper – with hydrogen peroxide, chrlorine oxide or oxygen to get that white, bright color.
If the recovered paper is colored, color stripping chemicals are used to remove the dyes from the paper. Oftentimes from this process, brown paper is obtained.
Now, that the pulp is cleaned up and prepped to go, it's ready to become paper again.
The fibres can be used alone or blended with new fibres. The pulp gets mixed with water and chemicals so that the pulp is 99.5% water. This watery pulp blend then goes through the headbox of a paper making machine which sprays a continuous jet of the stuff onto a huge wire mesh like screen.
On the screen, the water drains from the pulp, leaving behind the recycled fibres which bond together to form a sheet. This sheet is then passed through a series of felt-covered press rollers which squeeze out additional water. The sheet – which is now watery paper then passes through a series of heated metal rollers which dry the paper completely. Depending on whether or not the paper requires coating (i.e. the paper is set to be smooth, glossy, etc.) then this coating mixture is applied at the end of the process.
Finally, the finished paper is would into a huge role and removed from the machine. From there the paper is cut into smaller rolls or into sheets.
Tada! Recycled paper!